"Swap default styles in instances"

Hi community members, After I tried the swap library feature on Figma, I have confused about the “Swap default styles in instances” option. I have read the guideline from Figma, but it didn’t help. I don’t know the difference between checking or unchecking this option. I even try to test this function by creating a mockup file to test, but it is still not clear to me. Can anyone demonstrate this thing or explain it to me more?